The present invention relates generally to agricultural machines and more particularly to an apparatus for controlling a transfer device on an agricultural machine such as a self-propelled forage harvester. The transfer device transfers crop from the agricultural machine to a transport receptacle.
European patent document EP 0 131 693 A1 discloses a control system for a discharging connector. The apparatus described relates to an agricultural harvester towing a transport receptacle via a hitch. By means of the connector, the chopped crop is transferred from the agricultural harvester to the transport receptacle. The relative angle between the hitched transport receptacle and the agricultural harvester is detected at the coupling point. With reference to this angle, the connector is controlled according to a given program in such a way that the crop always enters the transport receptacle. The relative angle between the connector and agricultural harvester is determined and conveyed to a control system.
A disadvantage with this apparatus is that the relative angle between the agricultural harvester and the hitched transport receptacle must be detected. Mechanical sensing devices without play and with high-resolution sensors, or optical scanning means are necessary. When the transport receptacle is loaded with crop, it is unhitched and replaced with an empty transport receptacle. The mechanical sensing device must be recoupled and adjusted. For an optical scanning device, it is necessary for each transport receptacle to be fitted with a corresponding reflector means.
German patent document DE 44 03 893 A1 discloses an apparatus for filling transport receptacles, a control system for a transfer device and a limit switch contact means to control prefixed relative angle positions of an upper discharge chute to the longitudinal direction of the agricultural harvester. The transfer device is controlled with the aid of optical or acoustic distance measuring devices which determine and measure the degree of filling of the transport receptacle. The degree of filling of the receptacle is determined by several sensors near the instantaneous crop impingement point on the transport receptacle by means of distance signals. When a given level is reached, the transfer device is pivoted until an adjacent point which exhibits a lower level is detected.
A disadvantage of this transfer control system is the very expensive distance sensors. Moreover, this apparatus only works satisfactorily when the crop stream is approximately spewed in the direction of the distance measuring device (i.e. when the crop stream is approximately perpendicular to the transport receptacle floor). If the crop is transferred to a transport receptacle hitched to a self-propelled agricultural harvester or trailed behind the agricultural harvester by a towed receptacle, this loading apparatus fails. The failure is caused by the direction and transfer distance between the discharge point and transport receptacle. The crop does leave the transfer device almost horizontally, but with increasing transfer distance, the crop stream will become slower and assume a curved trajectory. The distance measuring devices function with reference to the direction of ejection preset by the transfer device. Due to the curved trajectory of the crop stream, the point of impingement of the crop on the transport receptacle and the region detected by the distance measuring devices are different. This error results in unsatisfactory control.